A "classic" tap-hole drilling machine has a supporting structure in which a cantilever arm is swivellably mounted with a first end about a first axis. A swivel drive produces a swivelling motion of the cantilever arm about this first axis, e.g. from a rest position to a first working position in front of a first tap-hole, or to a second working position in front of a second tap-hole, and back to the rest position in each case. A drill mounting is connected to the second end of the cantilever arm and can swivel about a second axis. A control rod is connected via a first linkage to a fixed point on the supporting structure and via a second linkage to the swivellable drill mounting, so that a swivelling motion of the cantilever arm about the first axis produces a swivelling motion of the drill mounting about the second axis. The alignment of the drill mounting can consequently be determined by the control rod, as a function of the angular position of the cantilever arm.
The drawback with such swivelling devices is that the control rod crosses the cantilever arm when swivelling the drill mounting. Consequently, this control rod has to be arranged either above or below the cantilever arm, which of course increases the space required to swivel the cantilever arm (i.e. the headroom required). This can lead to space problems, particularly when a tap-hole drilling machine and a tap-hole plugging machine are arranged on the same side of the tapping runner and the cantilever arm of the tap-hole drilling machine has to pass under or over the tap-hole plugging gun when swivelling. Such a configuration is described in U.S. Pat. No. 4,195,825, for example.
The task of the present invention is to create a swivelling device with a cantilever arm and control rod which requires less headroom to swivel the cantilever arm.